While David Petraeus's sexy email scandal has given us many things—a clearer picture of Petraeus's public relations machine, insight into the military-industrial-housewife complex, the understanding that 60-year-olds are no more responsible about sexy Internet use than are tweens—we still don't understand exactly where it came from. The best guess so far is that an unnamed shirtless FBI agent had a crush on a married Tampa socialite, and got the investigation going to impress her.

Think about what got the investigation started: Jill Kelley got between five and 10 harassing anonymous emails. They did not threaten violence. According to The Daily Beast's Michael Daly, they said things like, "Who do you think you are? … You parade around the base." Another email "claimed to have watched Ms. Kelley touching 'him' provocatively underneath a table," according to The Wall Street Journal. It's hard to imagine small town cops getting excited about those messages. When Kelley told her friend who worked at the FBI about them, the agency wasn't all that excited, either. The cyber squad in the Tampa field office "was not even sure the case was worth pursuing," Daly reports. "What tipped it may have been Kelley’s friendship with the agent. The squad opened a case, though with no expectation it would turn into anything significant."

At Slate, Emily Bazelon writes that given her reporting on cyberbullying, she doubts cops would have opened a case. Broad stalking and harassment charges "shouldn't trigger an investigation based on so little evidence," she says. But once it got going, it grew easily, thanks to outdated laws and new technology. The New Yorker's Patrick Radden Keefe notes there's a delicious irony in Petraeus being brought down by the national security capabilities he boasted about as "diabolical."

The FBI doesn't need a warrant to access email that's more than 180 days old, because a 1986 law declares that "abandoned," The New Yorker explains. Once they figured out it was Paula Broadwell sending the emails, they were able to go into Broadwell's email account, The Daily Beast reports, and discovered Broadwell "really knew Petraeus." The FBI figured out the two were leaving messages for each other in the drafts folder of a shared account, and that they were having an affair. That's when the investigation "morph[ed]" into an investigation into whether classified information was leaked, The New Yorker says. But despite concluding no crime had been committed, Slate notes, the FBI notified the Director of National Intelligence, James Clapper, anyway. Clapper asked Petraeus to resign. And still, the investigation keeps going, with the FBI raiding Broadwell's house Monday night. On Tuesday, it was revealed that Gen. John Allen was emailing with Kelley, too, though there's no accusation that classified information was leaked in that case, and even the "flirtatious" nature of the emails is disputed. And we still don't know if Agent Shirtless ever managed to impress Jill Kelley.

(Photos via Associated Press, Reuters, and CelebMuscle via Flickr.)